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61.
Eleven farnesyl diphosphate analogues, which contained omega-azide or alkyne substituents suitable for bioorthogonal Staudinger and Huisgen [3 + 2] cycloaddition coupling reactions, were synthesized. The analogues were evaluated as substrates for the alkylation of peptide cosubstrates by yeast protein farnesyl transferase. Five of the diphosphates were good alternative substrates for farnesyl diphosphate (FPP). Steady-state kinetic constants were measured for the active compounds, and the products were characterized by HPLC and LC-MS. Two of the analogues gave steady-state kinetic parameters (kcat and Km) very similar to those of the natural substrate. 相似文献
62.
C. Miège A. Peretti P. Labadie H. Budzinski B. Le Bizec K. Vorkamp J. Tronczyński H. Persat M. Coquery M. Babut 《Analytical and bioanalytical chemistry》2012,404(9):2721-2735
The main objective of this study was to collect new data on the occurrence, levels of priority and emerging organic compounds in freshwater fish sampled in the Rhone River. The 34 studied contaminants included alkylphenols, bisphenol A, polybromodiphenylethers (PBDE), perfluorinated compounds, hexabromocyclododecanes (HBCD), hexachlorobenzene and hexachlorobutadiene (HCBD). About 50 fish samples (individual specimens or pooled fish) were collected from three sites located upstream and downstream of the Lyon metropolitan area in the Rhone River (France). Four species were caught at each site, namely: the barbel (Barbus barbus), the common bream (Abramis brama), the white bream (Blicca bjoerkna) and the chub (Squalius cephalus). Some contaminants were quantified in all the 32 fish samples analysed: 4-nonylphenol, α-HBCD, the six PBDE congeners (28, 47, 99, 100, 153, 154), perfluorooctanesulfonate (PFOS) and perfluorodecanoic acid. Twenty three of the 32 samples had a concentration of PFOS above the Environmental Quality Standards (EQS) (up to six times higher than the EQS), and all the 32 samples had concentrations of PBDE above the EQS (up to 4,000 times higher, with the sum of six PBDE varying from 4.5 to 182?ng/g dry weight). Clearly, the interest to consider PFOS and HBCD as new priority substances is confirmed. In contrast, the pertinence of a priority status for HCBD, which was never quantified in our study, might have to be reconsidered in the future. 相似文献
63.
Jeff W. Labadie James L. Hedrick 《Journal of polymer science. Part A, Polymer chemistry》1990,28(12):3467-3480
Phenylquinoxaline–aryl ester block copolymers were synthesized using well-defined phenolic hydroxyl terminated oligomers via a monomers/oligomer approach. Phenylquinoxaline oligomers with molecular weights of 5600 and 12,900 g/mol were prepared from the condensation of 1,4-bis(phenylglyoxalyl)benzene and 3,3′-diaminobenzidine in the presence of 4-hydroxylbenzil. The oligomers were copolymerized with isophthaloyl chloride and bisphenol A in tetrachloroethane to afford the desired phenylquinoxaline–aryl ester block copolymers. Copolymers with polyester compositions ranging from 15–50 wt % were prepared by controlling the monomers/oligomer stoichiometry. The majority of the materials displayed single phase morphologies with Tgs intermediate to the Tgs for the poly (phenylquinoxaline) and polyester homopolymers. Plots of the reciprocal of the Tg of the copolymers versus composition agreed well with values predicted by the Fox equation. A multiphase morphology was obtained for the copolymer with the highest polyester block length (? 13,000 g/mol), which displayed a Tg at 190 and 300°C indicative of a glassy–glassy system. Significant improvement in the elongations were observed for the copolymers relative to the poly(phenylquinoxaline) homopolymer. The improved elongations were obtained with minimal sacrifice to the modulus. These materials represent the first example of poly(phenylquinoxaline) block copolymers from well-defined phenylquinoxaline oligomers. 相似文献
64.
A general approach was developed for the regio- and chemoselective covalent immobilization of soluble proteins on glass surfaces through an unnatural amino acid created by post-translationally modifying the cysteine residue in a CaaX recognition motif with functional groups suitable for "click" chemistry or a Staudinger ligation. Farnesyl diphosphate analogues bearing omega-azide or omega-alkyne moieties were attached to the cysteine residue in Cys-Val-Ile-Ala motifs at the C-termini of engineered versions of green fluorescent protein (GFP) and glutathione S-transferase (GST) by protein farnesyltransferase. The derivatized proteins were attached to glass slides bearing linkers containing azide ("click" chemistry) or phosphine (Staudinger ligation) groups. "Click"-immobilized proteins were detected by fluorescently labeled antibodies and remained attached to the slide through two cycles of stripping under stringent conditions at 80 degrees C. GFP immobilized by a Staudinger ligation was detected by directly imagining the GFP fluorophore over a period of 6 days. These methods for covalent immobilization of proteins should be generally applicable. CaaX recognition motifs can easily be appended to the C-terminus of a cloned protein by a simple modification of the corresponding gene, and virtually any soluble protein or peptide bearing a CaaX motif is a substrate for protein farnesyltransferase. 相似文献